In a Schottky barrier diode (SBD), at an interface between a Schottky electrode made of metal and a semiconductor region, a work function difference between the metal and semiconductor is typically small. Because of the material property difference, a leakage current of the SBD may be relatively larger than that of a PN diode when the diodes are reverse-biased.
Japanese Unexamined Patent Application Publication Number 2000-294804 shows a semiconductor device having a JBS, in which a PN diode is disposed on a part of a Schottky junction to suppress a leakage current when reverse-biased. The semiconductor device having a JBS is described below with reference to FIG. 8. The semiconductor device includes a Schottky electrode J1, an N− type drift layer J2, a resurf layer J3, and P type layers J4. The P type layers J4 have a projected shape and stripe structure. The P type layers J4 are disposed in a surface layer of and an internal portion of the N− type drift layer 2. The p type layers J4 are disposed in an area located inside of the resurf layer J3 and an area located inside of a contact region between the Schottky electrode J1 and the N− type drift layer J2. The resurf layer J3 is included in a termination structure. The termination structure may function as a periphery part for voltage proof.
According to the JBS shown in Japanese Unexamined Patent Application Publication Number 2000-294804, since a depth of each p type layers J4 is substantially equal to that of the resurf layer J3, a depletion layer may be created near the p type layers J4 in a case of surge. A dot line in FIG. 8 shows a location of the depletion layer. In the above case, an electric field due to the surge is easier to concentrate at an area located around a boundary between the p type layers J4 and the resurf layer J3. Such electric concentration may cause failure of the semiconductor device. Symbols VIII shown in FIG. 8 indicate the location of the electric field concentration.